Teenagers are increasingly arming themselves with weapons to protect themselves against attacks in the street, according to a report by a leading children's rights advocate.

The recent string of murders of teenagers in London, Manchester and Liverpool has produced a "fear factor" among teenagers, who are responding by carrying weapons themselves, according to Roger Morgan, the children's rights director for England and author of the report, published by Ofsted. Carrying a weapon could be a "logical" response by children who fear for their safety on the street, he said.

The report, based on interviews and questionnaires involving more than 300 children in care and in boarding schools, suggested that they are also increasingly facing cyber-bullying.

Some children questioned for the research suggested that police should be brought in to deal with bullying in the streets before it escalated into violent attacks. The report said: "Some discussion groups told us that when bullying gets serious a growing way of young people showing that they can defend themselves is to carry a weapon, such as a knife or bottle."

Morgan told the Guardian: "Children now know examples of other children their age or who lived near who have been killed on the street for no reason. They can name individual children who they relate to. They are very aware of that context and that they don't always feel safe. And some are responding by saying to feel safe they need to think about protecting themselves. There is a huge fear factor out there." The report was applicable to society in general because the children attended normal schools and many lived in residential areas with foster carers, he said.

The report suggested that many children were experiencing bullying. Some 42% of children said they were last bullied by name calling, 25% reported "being hit" and 15% were beaten up.

The children's minister, Kevin Brennan, said: "This report is based on the individual opinions of a particular group of children and therefore too anecdotal to provide objective evidence of a trend."